Many light-emitting sources have light intensity distribution characteristics which are more conveniently depicted by a graph showing a variation of light intensity with reference to radial angles in lateral directions, as described for example in US 2006-0034097A1.
Semiconductor light-emitting devices are finding increasingly more applications in modern day electronic devices. Typical semiconductor light-emitting sources, for example, packaged light-emitting diodes (LED), are directional and have a characteristic optical axis along which light is propagated. Typically, the light intensity of an LED follows the Lambert distribution as depicted in FIG. 27 of US 2006-0034097A1. More particularly, a substantial portion of the entire light energy emitted by an LED is contained within an angular range centred about the optical axis and the angular range is commonly referred to as the “viewing angle” of an LED. The viewing angle ranges of an LED are typically between +/−15° to +/−60° about the optical axis.
In many applications involving the use of semiconductor light-emitting devices, it is desirable to condition the optical output of a plurality of light-emitting sources to suit various objectives.
For example, a liquid crystal display (LCD) is generally equipped with a backlight apparatus comprising an array of LEDs for illuminating an LCD panel from behind, since an LCD display panel is not self-illuminating. An example of such a backlight apparatus is described in US 2005-0243576A1.
In such or other similar applications, it is desirable to mix optical output from a plurality of LEDs, for example, LEDs of the three primary colours, red (R), green (G) and blue (B), to prepare for forward transmission. The mixing of light from a plurality of LEDs, for example, LEDs emitting the three primary colours is advantageous since, by separating the LEDs into a plurality of distributed locations, and then by mixing light from the plurality of distributed sources, problems associated with the high power dissipation and the consequential thermal loading of a high power discrete white LED can be alleviated. However, the typical distribution characteristics of a typical LED means that a relatively large distance, compared to the length of a display panel, is required for light mixing. Therefore, it will be highly desirable if there can be provided optical arrangements for reducing the light mixing distance between a plurality of LED.
An exemplary optical arrangement for conditioning outputs of an LED for forward transmission is described in U.S. Pat. No. 6,598,998. However, such an arrangement requires a double molding process. Another example of such an optical arrangement is described in US 2006-0034097A1. The lens of US 2006-0034097A1 has a relatively complicated structure and the light mixing distance is relatively long.
Therefore, it will be desirable if there can be provided lens and light-emitting assemblies which would mitigate shortcomings of the known art.